1. The White iPhone was announced. Could have easily waited to compare the two if you were on the fence.
2. A gift is still in its box and Apple can sell it as new. A month old phone can not be sold as new.
The gift can be given to a recipient, used for a week and the recipient sells their 3GS, then realizes the white is something they wanted all along and return it. Purely Hypothetical but not far fetched.
When Apple says you can "try it out for 30 days", and yes, they DO say those exact words in the store, that means try it out and return for any reason you want.
I still think the better route (if you can) is to add a line to your account, pay the ETF, and have both in front of you if your on the fence. That way you profit and still put the unwanted phone in the hands of someone who wants it.
Blonde Buddhist